1. Field of the Invention
The present invention relates to sputtering apparatuses and more particularly to a sputtering apparatus capable of changing a distance between a substrate and a deposition preventing plate used for forming a film on a liquid crystal display device, a semiconductor, a magneto-optical recording disk, a magnetic recording disk and so on.
2. Description of the Background Art
Sputtering apparatuses are conventionally used to manufacture liquid crystal display devices, semiconductors, magneto-optical recording disks, magnetic recording disks and so on. The sputtering apparatuses used for mass production thereof include two kinds of apparatuses, namely, in-line sputtering apparatuses for carrying a substrate together with its holder and cluster tool sputtering apparatuses for carrying only a substrate.
In an in-line sputtering apparatus, a plurality of processing chambers such as a loading chamber, an unloading chamber and a film forming chamber are successively arranged in a linear or U shape manner. A substrate is held by a holder. A plurality of substrate holders pass through the processing chambers parallel to the substrate surfaces to successively form films on the substrates.
In the apparatus, a plurality of substrates are generally held on one substrate holder and carried by moving the substrate holder. In the film forming chamber, a deposition preventing plate for covering part of a substrate and an apparatus mechanism portion is provided so that an unnecessary film is not deposited on the substrate other than its prescribed portion and in a vacuum container.
Accordingly, the substrate is carried more easily than when only a substrate is carried, and the substrate is carried at high speed. Thus, the in-line sputtering apparatus has superior productivity. However, a relatively large gap has to be provided to avoid contact between a substrate and the deposition preventing plate or between a substrate holder and the deposition preventing plate while the substrate is being carried. Due to the large gap, an unnecessary film is deposited on the substrate holder and in the vacuum container. When such an unnecessary film exists and peels off, the substrate is tainted and the quality of a sputtered film is lowered. Further, in order to prevent deposition of a film on a substrate holder driving mechanism for moving a substrate holder, a large number of various deposition preventing plates have to be provided, and they have to be exchanged and washed constantly. Thus, maintenance becomes difficult.
On the other hand, in a cluster tool sputtering apparatus, a middle chamber, which contains a robot operating in a vacuum at the center of the apparatus, is provided and a plurality of processing chambers such as a film forming chamber, a loading chamber and an unloading chamber are arranged around the middle chamber. A film is formed on a substrate that is stopped and accurately positioned in the film forming chamber. Accordingly, a deposition preventing plate can be arranged sufficiently close to the substrate so that a film is not deposited on the substrate other than its prescribed portion and in a vacuum container at the time of film formation.
Accordingly, deposition of a film on an unnecessary portion can be minimized, and maintenance becomes easy because the number of components of the deposition preventing plate can be reduced. However, the robot, which operates in a vacuum, at the apparatus center can basically carry only one substrate at a time and has a limit in its substrate carrying capability. Thus, productivity is limited.
In recent years, several new sputtering apparatuses of the two kinds have been proposed. These techniques are disclosed in Japanese Patent Laying-Open Nos. 4-137522, 6-69316, 8-3744, and 9-143733, for example.
These new sputtering apparatuses are common in that substrate holders called substrate carts, trays or substrate carriers are used and that substrates are carried parallel to the substrate surfaces. For film formation, the substrates are attached to the substrate holders and moved in each processing chamber according to the purposes.
However,the sputtering apparatuses, which are considered to be improvements on the conventional in-line sputtering apparatuses, have not solved conventional problems with the in-line sputtering apparatuses. That is, the gap for preventing contact between the substrate and the deposition preventing plate or between the substrate holder and the deposition preventing plate during substrate carriage are still set to a fixed distance. Therefore, the problem that an unnecessary film is deposited on the substrate holder or in the vacuum container has not been improved.